A new study suggests that Mexico's drug violence was so bad at its peak that it apparently caused the nation's male life expectancy to drop by several months.

Experts say the violence from 2005-2010 partly reversed decades of steady gains, noting that homicide rates increased from 9.5 homicides per 100,000 people in 2005 to more than 22 in 2010. That has since declined to about 16 per 100,000 in 2014.

The study published Tuesday in the American journal Health Affairs says "the increase in homicides is at the heart'' of the phenomenon, though deaths due to diabetes may have also played a role.

"The unprecedented rise in homicides after 2005 led to a reversal in life expectancy increases among males and a slowdown among females in most states,'' according to the study, published by Jose Manuel Aburto of the European Doctoral School of Demography, UCLA's Hiram Beltran-Sanchez and two other authors.

The study's authors found that life expectancy for males in Mexico dropped by about six-tenths of a year from 2000-2010.

The study found that in five Mexican states - Chihuahua, Sinaloa, Durango, Guerrero, and Nayarit - men lost an average of one year of life expectancy between 2005 and 2010, while in the border state of Chihuahua alone, the loss added up to a startling three years.

"The mortality rate for males ages 20-39 in Chihuahua in the period 2005-10 reached unprecedented levels,'' the study noted. "It was about 3.1 times higher than the mortality rate of US troops in Iraq between March 2003 and November 2006.''

By 2010, two-thirds of Mexican states had lower life expectancies than they did in 2000, despite improvements in some health care programs.

The decline largely occurred from 2005-2010. Mexico's offensive against drug cartels started in 2006. The study found men were 10 times more likely than women to be killed in the violence, which was dominated by executions, shootouts and turf battles carried out by Mexican drug cartels.

Juan Eugenio Hernandez, an epidemiologist at Mexico's Center for Information on Public Health Decisions, noted it was the first time life expectancy in Mexico had declined since the country's 1910-1917 revolution.

Hernandez, who was not involved in the Health Affairs study, wrote that "indeed, violence has had a big impact on life expectancy ... mainly in the male population in several northern Mexico states and in Michoacan,'' a state located in western Mexico.

He said researchers had warned the violence would impact longevity rates, which he said "haven't diminished since the Mexican Revolution.''

Mexico previously had long been on a steady, upward trend. Between 1940 and 2000, Mexicans gained an average of four years in life expectancy per decade.

But in comparison with other Latin American countries like El Salvador, Honduras and Venezuela, Mexico's homicide rate remains relatively low.

"It is likely that other Latin American countries have been experiencing even greater reductions in life expectancy from homicide,'' the authors noted.